1. Field of the Invention
The present invention relates to a cutting insert used for cutting processing of a metal material by being detachably attached to a tool body.
2. Description of the Related Art
A cutting insert disclosed in Japanese Patent Laid-Open No. 2007-175788 has an approximately polygonal plate shape, in which a breaker projection having a standing wall surface which stands upward from a rake face on at least one of its nose portions and also protrudes toward a tip end of the nose portion is formed, and the rake face connected at least to the whole of or a part of a circumference of the standing wall surface is constituted by a first rake face extending inward from a cutting edge and a second rake face extending inward continuously from this first rake face and continuing to the standing wall surface.
Two-stage rake angles, that is, a first rake angle and a second rake angle are formed on the nose portion of the cutting insert of Japanese Patent Laid-Open No. 2007-175788, and as a result, a concavity is formed in the nose portion of a chip breaker. Therefore, the cutting insert of Japanese Patent Laid-Open No. 2007-175788 is excellent in heat and crack resistance and is designed so as to be able to apply a tool material which is poor in heat and crack resistance such as cermet, to light cutting including so-called finishing cutting, in which a cutting amount and a feeding amount are both small. However, although the cutting insert in Japanese Patent Laid-Open No. 2007-175788 effectively functions from finishing to light cutting, there are many cases where the cutting insert does not function effectively in a cutting condition of heavy cutting. Therefore, the cutting insert of Japanese Patent Laid-Open No. 2007-175788 cannot handle the cutting conditions from light cutting to heavy cutting, with one cutting insert.